Analog Devices

The LT3791 is a synchronous 4-switch buck-boost LED driver controller. The controller can regulate LED current up to 52V of LED string with input voltages above, below, or equal to the output voltage. The constant-frequency, forced-continuous current mode architecture allows its frequency to be adjusted or synchronized from 200kHz to 700kHz. No top MOSFET refresh switching cycle is needed in buck or boost operation. With 60V input, 60V output capability and seamless transitions between operating regions, the LT3791 is ideal for LED driver applications in automotive, industrial, and even battery-powered systems.For new designs we recommend the LT8391: 60V synchronous 4-switch, buck-boost LED controller due to its numerous performance improvements over the LT3791.FeaturesLT3791OPEN LED PinLT3791-1Replaces OPEN LED Pin With C/10 Pin Termination FlagApplicationsAutomotive Head Lamps/Running LampsGeneral Purpose Lighting

The LT3795 is a DC/DC controller designed to regulate a constant-current or constant-voltage and is ideal for driving LEDs. It drives a low side external N-channel power MOSFET from an internal regulated 7.7V supply. The fixed frequency and current mode architecture result in stable operation over a wide range of supply and output voltages. Spread spectrum frequency modulation (SSFM) can be activated for improved electromagnetic compatibility (EMC) performance. The ground referred voltage FB pin serves as the input for several LED protection features, and also allows the converter to operate as a constant-voltage source. The maximum output current is set by an external resistor, and the output current amplifier has a rail-to-rail common mode range. The LT3795 also includes a separate input current sensing amplifier that is used to limit input current. The TG pin inverts and level shifts the PWM signal to drive the gate of the external PMOS. The PWM input provides LED dimming ratios of up to 3000:1, and the CTRL inputs provide additional analog dimming capability.APPLICATIONSHigh Power LED, High Voltage LEDBattery ChargersAccurate Current Limited Voltage Regulators

The LT3796/LT3796-1 are DC/DC controllers designed to regulate a constant-current or constant-voltage and are ideal for driving LEDs. The fixed frequency and current mode architecture result in stable operation over a wide range of supply and output voltages. Two ground referred voltage FB pins serve as the input for several LED protection features, and also allow the converter to operate as a constant-voltage source. The LT3796/LT3796-1 feature a programmable threshold output current sense amplifier with rail-to-rail common mode range. A separate high side amplifier is gain configurable with two resistors and can be used to regulate a second current or a voltage in combination with one of the FB pins. The PWM input provides LED dimming ratios of up to 3000:1.The LT3796-1 is optimized for a second output current regulation loop that can be enabled/disabled with a PMOS switch, either to drive a second LED string or to extend analog dimming range.ApplicationsHigh Power LED, High Voltage LED, Dual StringBattery and SuperCap ChargersAccurate Current Limited Voltage Regulators

The LT3797 is a triple output DC/DC controller designed to drive three strings of LEDs. The fixed frequency, current mode architecture results in stable operation over a wide range of supply and output voltages. The LT3797 includes an integrated DC/DC converter to produce a regulated 7.5V supply for the N-channel MOSFET gate drivers of the three channels. This high efficiency converter enables the part to operate from a wide input voltage range from 2.5V to 40V.The LT3797 is designed so that each converter can use the most suitable configuration to drive its LED load, whether step-up, step-down or a combination. Two key features enable this flexibility: first the LT3797 can sense output current at the high side of the LED string; and second, the voltage feedback pin, FBH, is referred to the ISP current sensing input. The CTRL inputs provide output current analog dimming capability. The TG drivers level shift the PWM signals to drive the gates of external LED-disconnect P-channel MOSFETs, allowing high PWM dimming range, and providing LED overcurrent protection and short-circuit protected boost capability.ApplicationsAutomotive and Industrial LightingRGB LightingBillboards and Large Displays

The LT3798 is a constant-voltage/constant-current isolated flyback controller that combines active power factor correction (PFC) with no opto-coupler required for output voltage feedback into a single-stage converter. A LT3798 based design can achieve a power factor of greater than 0.97 by actively modulating the input current, allowing compliance with most Harmonic Current Emission requirements.The LT3798 is well suited for a wide variety of off-line applications. The input range can be scaled up or down, depending mainly on the choice of external components. Efficiencies higher than 86% can be achieved with output power levels up to 100W. In addition, the LT3798 can easily be designed into high DC input applications.ApplicationsOffline 5W to 100W+ ApplicationsHigh DC VINIsolated ApplicationsOffline Bus Converter (12V, 24V or 48V Outputs)

The LT3799-1 is an isolated flyback controller with power factor correction specifically designed for driving LEDs. The controller operates using critical conduction mode allowing the use of a small transformer. Using a novel current sensing scheme, the controller is able to deliver a well regulated current to the secondary side without using an opto-coupler. A strong gate driver is included to drive an external high voltage MOSFET. Utilizing an onboard multiplier, the LT3799-1 typically achieves power factors of 0.97. TheFAULTpin provides notification of open and short LED conditions. The LT3799-1 offers improved line regulation over the LT3799, but is not designed for use with a TRIAC dimmer.The LT3799-1 uses a micropower hysteretic start-up to efficiently operate at offline input voltages, with a third winding to provide power to the part. An internal LDO provides a well regulated supply for the part’s internal circuitry and gate driver.Triac DimmableLED Current RegulatorLT3799Yes± 10%LT3799-1No± 5%ApplicationsOffline 4W to 100W+ LED ApplicationsHigh DC VINLED Applications

The LT3800 is a 200kHz fixed frequency high voltage synchronous current mode step-down switching regulator controller. The IC drives standard gate N-channel power MOSFETs and can operate with input voltages from 4V to 60V. An onboard regulator provides IC power directly from VINand provides for output-derived power to minimize VINquiescent current. MOSFET drivers employ an internal dynamic bootstrap feature, maximizing gate-source "ON" voltages during normal operation for improved operating efficiencies. The LT3800 incorporates Burst Mode operation, which reduces no load quiescent current to under 100µA. Light load efficiencies are also improved through a reverse inductor current inhibit, allowing the controller to support discontinuous operation. Both Burst Mode operation and the reverse-current inhibit features can be disabled if desired. The LT3800 incorporates a programmable soft-start that directly controls the voltage slew rate of the converter output for reduced startup surge currents and overshoot errors. The LT3800 is available in a 16-lead thermally enhanced TSSOP package.Protected by U.S. Patents, including 5481178, 6611131, 6304066, 6498466, 6580258.Applications12V and 42V Automotive and Heavy Equipment48V Telecom Power SuppliesAvionics and Industrial Control SystemsDistributed Power Converters

The LT3804 is a high efficiency step-down switching regulator with optocoupler feedback control for regulating multiple outputs in single-secondary winding isolated power supplies.The LT3804 contains an error amplifier and an optocoupler driver to regulate the first (main) output. For the second output regulation, the LT3804 contains a complete PWM controller to drive dual synchronous N-channel MOSFETs. With leading edge modulation, it operates with either current or voltage mode control of the primary side. The LT3804 is synchronized to the falling edge of the transformer secondary winding and can be used in single ended or double-ended isolated power converter topologies. A user selectable discontinuous conduction mode improves light load efficiency.True differential Kelvin sensing is used for each output feedback amplifier to achieve high regulation accuracy and design simplicity. Other features include soft start, current limit and power good flags.Applications48V Input Isolated DC/DC ConvertersMultiple Output Power SuppliesOffline ConvertersDC/DC Power Modules

The LT3837 is an isolated switching regulator controller designed for medium power flyback topologies. A typical application is 10W to 60W with the part powered from a DC supply.The LT3837 is a current mode controller that regulates an output voltage based on sensing the secondary voltage via a transformer winding during flyback. This allows for tight output regulation without the use of an optoisolator, improving dynamic response and reliability. Synchronous rectification increases converter efficiency and improves output cross regulation in multiple output converters.The LT3837 operates in forced continuous conduction mode which improves cross regulation in multiple winding applications. Switching frequency is user programmable and can be externally synchronized. The part also has load compensation, undervoltage lockout and soft-start circuitry.The LT3837 is available in a thermally enhanced 16-pin TSSOP package.ApplicationsIsolated Medium Power (10W to 60W) SuppliesInstrumentation Power SuppliesIsolated Medical Supplies

The LT3840 is a high voltage synchronous step-down switching regulator controller capable of operating from a 2.5V to 60V supply.The LT3840’s low quiescent current, when configured for user selectable Burst Mode operation, helps extend run time in battery-powered systems by increasing efficiency at light loads. The LT3840 uses a constant frequency, current mode architecture. High current applications are possible with large N-channel gate drivers capable of driving multiple low RDS(ON)MOSFETs.An integrated buck-boost switching regulator generates a 7.5V bias supply voltage for MOSFET gate drive and IC power allowing higher efficiency operation over the entire input voltage range and eliminating the need for an external bias voltage. An accurate current limit set point regulates the maximum output current. A current monitor reports the average output current.ApplicationsAutomotive SuppliesIndustrial SystemsDistributed DC Power Systems